Background: Investigation of vertical velocity and recovery times in harbour porpoise (time between dives) and potential relationship with dive depth (longer recovery times for deeper dives). Dive threshold = 5 m. Analysis on high resolution dataset (n=5).
Figure 1.1: Recovery time (time between end of dive t and dive t+1) according to depth class for the 5 porpoises (high resolution tags).
Recovery time increases with dive depth.
Figure 1.2: Individual recovery times according to depth class.
Similar pattern across individuals.
Figure 1.3: Recovery time (time between end of dive t and dive t+1) according to depth class for the 5 porpoises (high resolution tags).
Similar pattern across light phases.
Figure 1.4: Recovery time according to depth class and month.
Similar pattern across months.
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## Kruskal-Wallis rank sum test
##
## data: dat$recovery and dat$month
## Kruskal-Wallis chi-squared = 355.54, df = 5, p-value < 2.2e-16
Figure 1.5: Recovery time according to month for dives between 0-10 m.
##
## Kruskal-Wallis rank sum test
##
## data: dat$mean_reco and dat$month
## Kruskal-Wallis chi-squared = 5, df = 5, p-value = 0.4159
Figure 1.6: Recovery time according to month for dives between 10-20 m.
##
## Kruskal-Wallis rank sum test
##
## data: dat$mean_reco and dat$month
## Kruskal-Wallis chi-squared = 3, df = 3, p-value = 0.3916
Figure 1.7: Recovery time according to month for dives between 20-50 m.
##
## Kruskal-Wallis rank sum test
##
## data: dat$mean_reco and dat$month
## Kruskal-Wallis chi-squared = 4, df = 4, p-value = 0.406
Figure 1.8: Recovery time according to month for dives between 50-100 m.
##
## Kruskal-Wallis rank sum test
##
## data: dat$mean_reco and dat$month
## Kruskal-Wallis chi-squared = 4, df = 4, p-value = 0.406
Figure 1.9: Recovery time according to month for dives between 100-400 m.
##
## Pearson's product-moment correlation
##
## data: sum2$maxdep and sum2$recovery
## t = 128.22, df = 247475, p-value < 2.2e-16
## alternative hypothesis: true correlation is not equal to 0
## 95 percent confidence interval:
## 0.2458876 0.2532765
## sample estimates:
## cor
## 0.2495857
Figure 1.10: Correlation between recovery time and max depth.
Both variables are highly correlated(cor test: 0.56, p<0.001).
Figure 2.1: Recovery time (time between end of dive t and dive t+1) according to dive durtaion for the 5 porpoises (high resolution tags).
Recovery time increases with dive duration, but breaking point around 1 min.
Figure 2.2: Individual recovery times according to dive durtaion.
Similar pattern across individuals.
Figure 2.3: Individual recovery times according to dive duration.
## [1] 17.40985
## [1] 6.70212
On average 17 (SD: 6.6) dives performed per hour, including 3.3 (SD: 1.2) dives between 0-20 m and 3.8 (SD: 1.7) dives deeper than 100 m. Note dives shorter tan 20 sec and shallower than 5 m were discarded.
Figure 3.1: Mean daily number of hourly dives according to max depth (dive threshold: 5 m).
Shallow dives above 20 m dominate (>10 per hour), and no clear pattern is evidenced as these dives are performed all day long. Dives between 20-50 m are performed mostly during daytime, especially for individuals 22850b, 27262 and 93100. Dives deeper than 50 m are less frequent (<5 dives per hour), and a clear diel pattern was observed as these deep dives get more frequent at night, especially for individuals 22850b, 27262 and 93100.
Figure 3.2: Mean daily number of hourly dives according to max depth (dive threshold: 5 m).
Figure 3.3: Porportion of hourly dives according to max depth.
Figure 3.4: Mean daily number of hourly dives according to max depth and months (dive threshold: 5 m).
Figure 4.1: Average ascent rate (m/s) according to depth class.
Ascent rate is higher at greater depths.
Figure 4.2: Average ascent rate (m/s) according to depth class and month.
Figure 4.3: Average descent rate (m/s) according to depth class.
Similar pattern for descent rate higher for deeper dives.
Figure 4.4: Average descent rate (m/s) according to depth class and month.
Figure 4.5: Vertical speed (m/s) according to descent (orange) and ascent (green) phase and depth class.
## # A tibble: 25 × 3
## # Groups: id [5]
## id class mean_bottom_time
## <chr> <fct> <dbl>
## 1 22849b (0,10] 0.197
## 2 22849b (10,20] 0.228
## 3 22849b (20,50] 0.324
## 4 22849b (50,100] 0.476
## 5 22849b (100,400] 0.335
## 6 22850b (0,10] 0.216
## 7 22850b (10,20] 0.220
## 8 22850b (20,50] 0.336
## 9 22850b (50,100] 0.552
## 10 22850b (100,400] 0.361
## # … with 15 more rows
Figure 5.1: Individual bottom duration (in min) according to depth class.
Bottom time increases with dive depth until 100 m, but then decreases for dives deeper than 100 m.
Figure 6.1: Average ascent rate (m/s) according to dive type.
Figure 6.2: Average ascent rate (m/s) according to dive type and month.
Figure 6.3: Average descent rate (m/s) according to dive type.
Figure 6.4: Average descent rate (m/s) according to dive type and month.
Figure 6.5: Vertical speed (m/s) according to descent (orange) and ascent (green) phase and dive type.
ADL estimated at 5.4 min for a 28 kg porpoise (Reed et al 2000).
ADL estimated at 4.5 min for a 37 and 48 kg porpoise (Otani et al 2000).
Range of ADL estimated: 2.2-5 min (using body mass & metabolic rates from Rojano-Donate et al 2020).
ADL estimated at 2.2 min for a 26 kg porpoise (McDonald et al 2021). ADL estimated at 3.0 min for a 30 kg porpoise (McDonald et al 2021). ADL estimated at 4.2 min for a 44 kg porpoise (McDonald et al 2021). ADL estimated at 6.3 min for a 67 kg porpoise (McDonald et al 2021).
Figure 7.1: Descent rate according to max depth for deep dives (type 3).
Figure 7.2: Descent rate according to dive duration for deep dives (type 3).
Figure 8.1: Ascent rate according to max depth for deep dives (type 3).
Figure 8.2: Ascent rate according to dive duration for deep dives (type 3).